[tor-bugs] #16352 [Applications/Tor Browser]: Play with Intel's MPX for hardened Tor Browser builds

[Tor Bug Tracker & Wiki]

#16352: Play with Intel's MPX for hardened Tor Browser builds
------------------------------------------------+--------------------------
 Reporter:  gk                                  |          Owner:  tbb-team
     Type:  task                                |         Status:  new
 Priority:  Very High                           |      Milestone:
Component:  Applications/Tor Browser            |        Version:
 Severity:  Normal                              |     Resolution:
 Keywords:  tbb-security, TorBrowserTeam201711  |  Actual Points:
Parent ID:                                      |         Points:
 Reviewer:                                      |        Sponsor:  Sponsor4
------------------------------------------------+--------------------------

Comment (by arthuredelstein):

 Here's what I have done with MPX so far:

 I have been using an MPX-supporting VPS and confirmed with a simple test
 program that `gcc -fcheck-pointer-bounds -mmpx` produces a binary that
 catches heap buffer overflows at runtime. Using CFLAGS and CXXFLAGS in
 mozconfig, and upgrading to the latest version of the gold linker, I built
 a big part of Firefox 52 using the same flags.

 But I'm currently running into the following error, which occurs only when
 the `-fcheck-pointer-bounds` flag is present in CFLAGS:
 {{{
  2:46.68 ../../../../build/unix/gold/ld: error: /home/arthur/tor-browser
 /obj-x86_64-pc-linux-gnu/config/external/nspr/pr/pripv6.o: re\
 quires dynamic R_X86_64_PC32 reloc against '_pr_test_ipv6_socket' which
 may overflow at runtime; recompile with -fPIC
  2:46.68 ../../../../build/unix/gold/ld: error: /home/arthur/tor-browser
 /obj-x86_64-pc-linux-gnu/config/external/nspr/pr/pratom.o: re\
 quires dynamic R_X86_64_PC32 reloc against '_PR_x86_64_AtomicAdd' which
 may overflow at runtime; recompile with -fPIC
  2:46.68 ../../../../build/unix/gold/ld: error: read-only segment has
 dynamic relocations
  2:46.68 collect2: error: ld returned 1 exit status
  2:46.68 /home/arthur/tor-browser/config/rules.mk:800: recipe for target
 'libnspr4.so' failed
  2:46.68 make[5]: *** [libnspr4.so] Error 1
  2:46.68 make[5]: Leaving directory '/home/arthur/tor-browser/obj-x86_64
 -pc-linux-gnu/config/external/nspr/pr'
  2:46.68 /home/arthur/tor-browser/config/recurse.mk:71: recipe for target
 'config/external/nspr/pr/target' failed
  2:46.68 make[4]: *** [config/external/nspr/pr/target] Error 2
  }}}

 I've tried a number of things to fix this error, including adding `-fPIC`
 to CFLAGS as well as NSPR_CFLAGS, but so far nothing has succeeded. I plan
 to continue to try to fix this bug and any remaining errors that turn up
 in the build, and then it should be possible to implement a patch for tor-
 browser-build.git.

--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/16352#comment:8>
Tor Bug Tracker & Wiki <https://trac.torproject.org/>
The Tor Project: anonymity online